This Coffee Tastes Like Dirt! It Was Ground This Morning.

Seattle loves its coffee, ensuring there are tons of used coffee grounds and stacks of burlap bags available all around town. Gardeners are the main beneficiaries of this surplus waste!

Used coffee grounds are a great source of nitrogen for your leafy plants and compost. You may notice that organic fertilizers include seed meal, which is nothing more than ground up seeds. Coffee is brewed from the seeds of coffee plants – making it seed meal too!

For a balanced compost, add some grounds to other nitrogen-rich “greens” (like fresh pulled weeds and grass clippings from lawns where pesticides or herbicides aren’t used), and carbon-rich “browns” (like fall leaves, ripped up newspaper and a little sawdust from non-pressure treated wood). There’s no exact recipe for compost, but about half greens and half browns by weight is the general rule. Compost materials should also have a good variety of textures to encourage air flow, so don’t just use fine materials like coffee grounds and sawdust. Mix them with other ingredients.

Many gardeners claim a light coffee mulch discourages slugs and other bugs from attacking their plants. The residual caffeine is repellent to some species, but apparently not earthworms. Gardeners also report that adding coffee grounds to soil feeds a profusion of earthworms. Your worm bin will benefit from occasional sprinklings of cooled moist grounds too, but don’t smother your workers with grounds! Keep a balanced bedding with other food sources.

If you mulch with grounds, remember they’re full of nitrogen – something fungus loves too. To prevent a fungal bloom, apply your coffee mulch thinly and not where it will remain soggy. A too-thick layer will also tend to shed water when the grounds dry out.

There is a lot of confusion among gardeners and chemistry dilettantes about the pH or acidity of coffee grounds. Though a cup of coffee is acidic, the used grounds are much less acidic, and certainly no more acidic than common peat moss soil amendments. If you have a small amount of cooled grounds from your morning coffee, you can safely spread them around without worrying about throwing off your soil’s pH. If you pick up a few bags of used grounds from Starbucks or another coffee shop, spread it around thinly or mix it well with plenty of compost material or soil. If you regularly apply lots of grounds to your garden, occasionally mix in a cup or so of garden lime or wood ashes from the fireplace. Coffee grounds are not recommended for house plants as trace salts may build up after repeated applications.

The best recommendation for using coffee grounds in your garden is to remember your mother’s admonition for moderation in everything. Don’t go crazy with coffee grounds, but as an amendment with compost and soil, you won’t go wrong recycling coffee grounds into dirt.

Copyright © 2007, Brian Ballard. All rights reserved.